Airline travel is a fraction of surface transportation.
Coal is the biggest carbon problem, followed by tar sands.
Tar sands, or oil sands, no matter what you call them, are loaded with sand.
Sand obviously is a leftover substance after the oil is removed. I am pretty sure they are not going to truck it back to Canada, and I doubt that it is the sort of sand you would put in the kids; sandbox, or use for concrete. It is probably pretty nasty stuff, and it will be left as close as possible to where it was extracted.
I have not heard what they do with it.